1. Field of the Invention
This invention relates to a semiconductor device. Especially it relates to providing semiconductor devices of integrated circuits (ICs) or large scale integrated circuits (LSIs). More particularly, it relates to a semiconductor device having electrode conductors formed of aluminum or aluminum-silicon alloy.
2. Description of the Prior Art
When an electronic circuit is constructed by connecting a transistor, diode etc. formed in a silicon semiconductor substrate, usually aluminum film conductors and a heat treatment are applied, after the interconnecting conductors have been formed, for the purpose of decreasing the contact resistance between the conductors and the substrate. The heat treatment is carried out at a temperature which does not cause the melting of the aluminum conductors, usually at about 400.degree. to 500.degree. C.
It is known that the silicon semiconductor substrates and the aluminum conductors diffuse into each other during the heat treatment. If aluminum diffuses up to the junction part which forms the transistor, diode, etc., the junction is broken and resultantly the intended electronic circuit cannot be constructed.
It is already known to use conductors of an aluminum-silicon alloy in which silicon contained corresponding to the solid solubility limit for aluminum or more, in order to prevent the mutual diffusion of the aluminum conductors and the silicon semiconductor substrate. However, a satisfactory result has not been obtained by this method.
Japanese patent Application Kokai (Laid-Open) No. 48,249/82 discloses to provide a titanium nitride layer at the interface between a silicon semiconductor substrate and an aluminum conductor to prevent the mutual diffusion of the two. Further, Japanese patent application Kokai (Laid-Open) No. 210,838/85 discloses to form a platinum silicide layer or a palladium silicide layer at the interface between a silicon semiconductor substrate and an aluminum conductor.
However, according to the study of the present inventors, when a titanium nitride layer is provided, it is ineffective unless it has a large thickness of about several .mu.m. If it has a small thickness of about 0.1 .mu.m aluminum and silicon diffuse into each other through the grain boundary of titanium nitride matrix. A thick titanium nitride layer of several .mu.m thickness is unfavorable because it causes an increase in contact resistance.
When a platinum silicide layer or a palladium silicide layer is provided, because it is prepared as described in Japanese patent application Kokai (Laid-Open) No. 210,838/85 by forming a platinum layer or a palladium layer on a silicon semiconductor substrate, then depositing silicon thereon and making the two react with each other, the production process is complicated and is not useful in practice. Further, the use of platinum or palladium causes an increase in the cost of the resulting semiconductor device.